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oscarmax avatar image
oscarmax asked

MPPT SmartSolar MPPT begineer confusion

Hi I very new to all this and find it confusing.

Earlier this year I fitted a 75/15 SmartSolar and battery sense to my caravan, I have a newish wet 12v leisure battery, everything has been working fine, but the battery has always been fully charge, at this time of the year I am usually getting 2 to 3 watts. My caravan is fitted with a 80 watt mono solar panel

Yesterday I cleaned the caravan it was dirty under the panel so I used a small brush to clean, in the process I move the wiring connector out of the way. I had to move the caravan so had to use the caravan mover, this obviously took some energy out of the battery.

Now the App on my iPhone is reading 0 watts and 22v and is in bulk mode, this morning it was reading 0 watt and 20.9v in bulk mode, I have a fuse from the solar panel to the MPPT controller, I removed and replaced the fuse it went into absorption mode. I have just checked again it has gone back into bulk mode 0 watt 19.9 v. The voltage is charging. Though out all this the caravan battery is recording 12.84 volts.

Have I cause a problem with the solar connectors or all of this normal ?

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klim8skeptic avatar image klim8skeptic ♦ commented ·

You might want to specify which voltage readings relate to the solar pv voltage, and battery voltage.

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oscarmax avatar image oscarmax commented ·

Solar 20/22v caravan habitation battery readings 12.84v

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3 Answers
Justin Cook avatar image
Justin Cook answered ·

@Oscarmax, usually a 0A reading from PV (under good sun conditions) is caused by either a blown fuse at the battery (since you should have a fuse at the battery on the POS line between the SCC and the battery) or reversed polarity at the SCC on the PV input - so those are things to check right away.

That being said, it appears that your battery is already full (12.84v), so that could easily explain what you're seeing as well. A way to test this will be to put a load on your battery (inverter or some other significant load) and see if your solar harvest current readings ramp up to compensate for the current out of the battery.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

Also check the fuse at the MPPT itself. ;)

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oscarmax avatar image oscarmax commented ·

I finally solved the problem, it was a blown fuse to the caravans habitation battery, I had fitted a new fuse box and labelled the connection up wrong, I an feeling a bit stupid now. Anyway thankyou all for the help.

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oscarmax avatar image
oscarmax answered ·

Hi Justin it is very overcast in the UK, I just assumed after using the caravan motor mover it would have used up some of the energy in my acid wet battery.

I will put some load on the battery tomorrow (hopefully we may have some sun) and see what happens.

Following advise from you guys on the forum I have made sure my controller, solar and battery are well fused and easily accessed.


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oscarmax avatar image
oscarmax answered ·

We I put this system underload midday, I turned the ceiling extractor fan onto full blast, it draws about 3-4 amps. Solar panel fluctuating slight averaging 19.7v under load the caravan battery dropped down to 12.6 v, then not under load recovered straight away to 12.78v. Still recording 0watts

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

Where do you read the battery voltage? VictronConnect? Can you make a screenshot or a photo?
Have you checked all fuses?

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oscarmax avatar image oscarmax Matthias Lange - DE ♦ commented ·

I am using my iPhone Victron APP and the caravan display panel, I have checked all my fuses, and used my circuit tester at connection, I have a funny feeling when I cleaned the panels and move the connectors out of the way I may have created a poor connection.

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oscarmax avatar image oscarmax oscarmax commented ·

I have just been out to the caravan with my tester, its is 2 pm in the UK overcast and raining, double checked the MPPT fuse ok, checked reading from MPPT solar connection terminals recording 19.6v, took a reading at the MPPT battery and load terminals 16.6v, still 0watts habitation battery using iPhone APP and caravans display 12.76v

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ oscarmax commented ·

Did you also checked this fuse?

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mppt7515fuse.png (393.2 KiB)
oscarmax avatar image oscarmax oscarmax commented ·

yes I have checked its ok

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ oscarmax commented ·

Can you make a screenshot of VictronConnect?

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oscarmax avatar image oscarmax Matthias Lange - DE ♦ commented ·

No I am not that switched on

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